Field of the Invention
The present disclosure relates to the field of power electronics, and more particularly, to a resonance-type contactless power supply and power receiver.
Description of the Related Art
Contactless power supply is widely used in electronic products, especially in low-power electronic products such as cellular phones, MP3 players, digital cameras, laptop computers, and the like, due to their convenience and availability. A conventional contactless power supply typically includes a transformer having a transmitting coil L1 and a receiving coil L2, and electric energy is typically transferred from a power transmitter to a power receiver by magnetic coupling between a primary coil and a secondary coil of the transformer.
During transmission of electric energy, inductance values of the transmitting coil and the receiving coil may be changed by the factors such as external obstacles (for example, a magnetic conductive object), a load of the power receiver, variations in an operating temperature of the circuit, and variations in locations of the coils. As a result, a resonance frequency of the resonance circuit is changed by variations in the inductance values of the transmitting coil and the receiving coil, and detuning occurs, which decreases significantly a transmission efficiency of the system.
The conventional wireless power supply system basically operates at a self-inductance resonance frequency of the system. The self-inductance resonance frequency of the system is a frequency at which impedances of a capacitor and self-inductance of a coil can be canceled out in the transmitter and the receiver. However, when operating at the self-inductance resonance frequency, the receiver will provide an unstable current to the load, have a low transmission efficiency, and introduce a complex control scheme.